I never use this term, but almost everyone else uses it to describe my approach. Fair enough. My view is that science, indeed all of knowledge, forms a system that rests on a single basis. In other words, there has to be something, some bedrock on which everything we know rests. If that foundation is not absolutely solid, then the whole structure can never be secure. (I never did too much building—manual labor was really not my thing—but this much I've picked up.)
So, anyway, given that I want to construct a system of knowledge that will endure forever, my initial interest is in that foundation. What does it mean for there to be a foundation of science that is completely unshakeable? Part of my genius (only a small part, to be sure) is that I find a clear way to ask that question—and then to answer it.
If you have read my Meditations (and who hasn't, really?), you will have observed—in addition to the beauty of the prose—that in the first part of the book I cast doubt on all of our ordinary beliefs. Some people conclude that I am therefore an extreme skeptic. Now, I do not like to insult those who misunderstand me, so I will here use a little known French world to describe those who hold such a view: idiots!
I am not a skeptic, since I do not deny the possibility of knowledge. No, I am French, and therefore I love knowledge—she is very beautiful. In fact, I love knowledge so much, I want it to be certain, unshakeable—and so I employ my method of doubt, or what is sometimes referred to as "methodological skepticism." That is, for the purposes of achieving certain knowledge, I propose that any claim that can be at all doubted will be cast aside just as if it were false.
The goal is to see if there is any belief that can withstand the most extreme doubt. That belief, if it exists, will by definition be indubitable, and only such a belief can serve as the secure foundation for an enduring system of knowledge—which is what I put forward in the end. That's not the goal of a total skeptic, right?
Everyone knows my statement "I think, therefore I am." (The problem is they don't seem to know anything else I said.) Now, the Latin for "I think, therefore I am" is "Cogito ergo sum." A lot of people think I say this in my Meditations, but I actually saved it for a lesser-known work called the Principles of Philosophy.
These days, everyone uses the term "cogito" as a way of referring to my argument that I, as a thinking substance, necessarily exist. Translation: because I think, I can be sure that I exist. Not my terminology, really but hey, I don't mind; as long as people don't think it's some new dance move (and tell Miley Cyrus to try doing it), I'm okay with it.
This is the standard I rely on to determine whether or not something is true. How do I know that I necessarily exist, or that there is an absolute distinction between minds and bodies? Why, because I conceive these ideas clearly and distinctly, of course. It's true because I totally understand it.
Now, that may sound a little arbitrary, but remember: I'm a mathematician, so I'm used to relying on this principle in order to determine that a proof is valid. Why is it that I know that the angles of a triangle must add up to 180 degree? Simply because I understand this idea clearly and distinctly. As a philosopher, I use exactly the same principle, though I maybe extend it just a little bit further than the average mathematician.
I'm not sure I should be even telling you about this one, since it makes me look pretty bad. But in the interests of fairness (not that I've ever been interested in that before), here goes. The Cartesian circle is an alleged logical fallacy I commit that invalidates my whole philosophical system. I get a little faint even thinking about it.
What's the problem? Well, you remember my idea of clear and distinct cognition? I rely on clearness and distinctness many times in my writing, but especially in my proof of God's existence—that's how I know that the key principle I rely on in this proof is true.
Well, after I have proven God's existence, I go on to show that the goodness of God ensures that anything I perceive clearly and distinctly must be true. After all, if that were not the case, then God would be a deceiver, but I have shown that he exists, and that he is perfectly good.
Do you see the problem? (I admit I didn't, or else I wouldn't have made the argument in the first place.) The problem is that the argument is circular! In order to establish the truth of the principle I use to prove God's existence, I have to already assume that God exists. So I haven't really proven anything at all.
And it gets even worse—if possible. I appeal to God in order to prove the existence of the external world and everything in it: I argue that God would be a great deceiver if he gave me every reason to believe there is an outside world and yet have this belief be false. So without God's existence, my entire system falls apart. I end up with no external world, no bodies, no physics—nothing. How could I have been so stupid? I hate myself; I hate myself!
Or maybe—just maybe—I have some very clever way of getting around this objection. I will leave it to my interpreters to work that one out.
This is a second, shorter argument I offer as proof of God's existence in my Meditations, my Principles of Philosophy, and elsewhere. In fact, it is a variation of an argument that had been put forward in the 11th century by a philosopher named St. Anselm.
But I like my version much better.
It's very simple. I find in my mind an idea of God—that is, of a supremely perfect being. That idea must actually exist, otherwise I wouldn't be able to have an idea of a perfect being. After all, "existence" is one possible perfection, and a being who lacked existence could not be perfect. So the idea of a nonexistent perfect being is a logical contradiction, every bit as much as the idea of a triangle whose angles do not add up to 180 degrees.
Therefore, God's existence follows from the very idea of God.
If you think that's a silly argument, you've got a lot of company there. But just try and find the flaw. Go ahead—I dare you.
This is a distinction I draw in my first argument for God's existence in the Meditations. Somehow, everyone seems to get confused by it.
I will make it very simple. When we talk about "formal reality," we are talking about a thing's level of reality or, better, a thing's perfection. Some things have more formal reality than others because some things would seem to be more perfect (or more complex) than others. So, for example, if a human being is more perfect than a stone, then a human being can be said to have more formal reality than a stone has. Easy peasy.
We then come to objective reality. Objective reality is something that only ideas have. When we speak of an idea's objective reality, we are talking about an idea in relation to its object—i.e., to what it represents or what it's about. So, an idea's level of objective reality is determined by the level of formal reality of what it represents. The idea of person has more objective reality than the idea of a stone, for example.
Now, if this were a logic class, this would be the point at which the professor would begin to talk faster and faster and to write long, indecipherable equations on the board. And, almost against your will, you would feel your eyes begin to glaze over. But, don't worry— this is Shmoop. We write slowly and give lots of examples.
All I'm saying here is this: imagine you have two ideas in your head, one of a man, the other of a stone. I hold that the idea of a man has more objective reality than the idea of a stone. And the reason, of course, is that an actual man has more formal reality than an actual stone does. That's all there is to it.
Just try to remember this distinction, since I rely on it in order to prove God's existence.
So, big question: how do the mind and the body interact?
You might say: "That may have been a problem back in your day, Descartes. But that's just because you didn't have enough information on how the brain operates. We've got neuroscience now to work out all the details for us." That response—which I get a lot these days—only shows how little you understand of my thinking.
What you fail to grasp is that the brain is not the mind. The brain is a physical organ and, as such, is part of the body. The essence of the body and of all physical things is just to be "extended"—that is, to take up position in space. But what I show is that the mind is a completely immaterial or non-physical, non-extended entity, an entity whose sole property is to think.
Now, we know that the mind and body interact all the time. If I think that I want to raise my hand and then I raise my hand, my mind has caused my body to move. If I stub my toe and then feel intense pain, my body has caused an event in my mind.
But how is this possible? How can there be any sort of causal interactions between the mind and the body when the two seem to have absolutely nothing in common? (It sounds like the plot for a bad romantic comedy, which in a way it is.) Neuroscience can't help us here.
My solution is that the interaction between the mind and body takes place through the pineal gland, which is an extremely small organ in the brain. Now, I admit that this was not my most brilliant insight ever (but, as they say, even Homer nods). After all, the pineal gland may be small, but it's still a physical thing. So if there is a problem explaining how the mind and the body interact, then there is going to be the same problem in explaining how the mind and the pineal gland interact.
Somehow, I missed that.
Of course, none of my successors missed my little error. Instead, I am told that every last one of them tried his hand at coming up with his own precious solution to the mind/body problem. Their steady string of failures shows that it's a bit harder than it looks.